Closing the Loop in Adults With Type 1 Diabetes

People with type 1 diabetes(T1D) need regular insulin injections or continuous delivery of insulin using an insulin pump in order to keep the blood glucose levels normal. We know that keeping blood sugars in the normal range will help prevent long term diabetes related complications involving the eyes, kidneys and heart. However, achieving treatment goals can be very difficult as the tighter we try to control blood glucose levels, the greater the risk of the person developing episodes of low glucose levels (hypoglycaemia). This is a particular problem at night and one solution is to develop a system whereby the amount of insulin injected is very closely matched to the blood sugar levels on a continuous basis. This can be achieved by what is called a "closed loop system" where a small glucose sensor placed under the skin communicates with a computer containing an algorithm that drives an insulin pump. This system is being developed in Cambridge and we have trialed this on 16 children and adolescents with T1D in a clinical setting over the past year. We have found that this system is very effective at preventing hypoglycaemia in this group of patients.

We will recruit 12 adults with T1D on insulin pump therapy, and the studies will be done in a clinical research facility. The subjects will be studied on two nights. On one night they will have their normal insulin pump therapy and on the other night their insulin pump will be varied according to information about blood glucose values from the continuous glucose sensor. This information will be manually typed into the computer every 15 minutes from 8pm until 8am. The algorithm will advise of the insulin infusion rate and this will be manually changed by a trained nurse every 15 minutes throughout the night.

Inclusion criteria

• Type 1 diabetes, as defined by WHO for at least 6 months or confirmed C-peptide negative.
• On insulin pump therapy for at least 3 months

Exclusion criteria

• Non-type 1 diabetes mellitus
• Any physical/psychological disease likely to interfere with the study
• Taking medication likely to interfere with interpretation of the results
• Known/suspected allergy against insulin
• Patients with clinically significant nephropathy, neuropathy or retinopathy as judged by the investigator
• Ongoing severe recurrent hypoglycaemia as judged by the investigator.